The present invention is directed to a portable chair that is very light in weight and collapsible into a narrow bundle like an umbrella, in order to allow it to be easily carried in a backpack, slung on one's back in a small carrying-bag, carried by hand, etc., while being easily and readily erected for immediate use for supporting a person very securely and comfortably in a sitting position. Examples of prior-art collapsible chairs are numerous. One such chair is shown in U.S. Pat. No. 3,124,387 - Maclaren. The chair disclosed in this patent, like other prior-art chairs, is collapsible by folding the chair laterally and inwardly, which is achieved by scissor-linkages in the front, rear and sides of the chair. However, this chair, like other prior-art chairs, is intrinsically heavier and more complex than the present invention, while adding nothing to the comfort of the sitter.